LTO Starter Battery

[Julez]

Hello! the following question reached me.

Hey Julez, I was wondering about your BMS choices for the LTO battery. I was actually considering a 6S build with no BMS. It looks like you are using multiple technologies to balance cells. Can you point me to a blog post that explains the differences?

Cool stuff. Thanks for sharing.

I figured I answer here for the benefit of everyone.
I would not recommend to use an LTO battery completely without balancing, or any Li-based battery in general without it.
My approach is a bit over the top though, so not everything I did is really needed.
What I advise to use is a "capacitive active equalizer".
Choose "6s LTO":

https://de.aliexpress.com/item/4000241881122.html

These PCBs can be set for "LTO" via a solder bridge, and can be switched on via another solder bridge. This is important: The board draws an idle current of 15mA, which is too much for my liking. So I connected the "on" solder bridge pads to a 12V relay which is normally open (off). I connected this relay to the "D+" terminal of my alternator. Maybe the name for that terminal is different in Germany, but it has around 12V output only when the engine is running, and no output when it is stopped. This way, the balancer PCB is only on when the engine is running, and does not slowly deplete the battery when not.
It is important to bundle all cable accurately and apply strain relief. 80% of all machinery defects are because of metal fatigue, and this includes cables vibrated to shreds.

I also used such an "inductive active equalizer":

https://de.aliexpress.com/item/1005002579001608.html

But those are not terribly accurate, and not really needed if you have the capacitive one. At least their idle current is negligible.

Third I used is this passive balancer:

https://de.aliexpress.com/item/1005002461300483.html

This just starts to discharge cells slowly if they reach 2,7v or more. This is not bad to have, but if any cells reach such a high voltage, something is wrong anyhow. You can do without, but at such a low price, I would use it just because.

What I recommend is to charge the pack slowly to a good 15 or 15,5V before putting it in the car. This way, all the cells can be balanced at a low current, and one does not risk any cells overcharging if the pack was built from cells with uneven states of charge.

I also recommend adding a "diagnosis port", where you can measure the voltage of every single cell. I used a 7 contact female row header in my battery. With a little 2-contact adapter (male rov header) to a multimeter one can check quickly once in a while if all cells are all equal.

Another important aspect is to not connect these cells using bare copper sheetmetal. Aluminium and copper pressed together will form nasty stuff in an electrical connection leading to hotspots and failure and general doom. So I used "Cupal" washers between the cells and my copper connectors:

Cupal – Wikipedia

de-m-wikipedia-org.translate.goog

Cupal-Scheiben | Klauke

Cupal-Scheiben

www.klauke.com

Regards,
Julian

 

[Julez]

I don't know how to edit posts, but I still want to add some info about aluminium-copper connections.
In eastern Germany, because of socialism, copper was one of many things in short supply, so they resorted to aluminium wiring in many buildings. This leads to problems to this very day, so we have developed a bit of an expertise in this regard. Here is some more information:

Correctly connecting al and cu | Klauke

The technical report provides information about electrical installation, this technical report is about connecting aluminium and copper correctly.

www.klauke.com

Kupfer und Aluminium richtig kontaktieren

Korrosion an Kontakten zwischen Kupfer und Aluminium

www-strom--linie-eu.translate.goog

 

[Phoenix666]

I would like to mention, as I don't think it was in this thread, and I did not mention it.... There is another way to fry your Alternator. If your BMS cuts the battery from the alternator, there is a possibility that as the load drops dramatically, the voltage spikes massively, thus burning out the diodes in the alternator and possibly sending significantly high voltage through your entire system.

This is not an issue for me, as a BMS is not needed in my setup. (I never thought I would say that...)
Still, it is worth knowing, if you were to use LiFepo4.
After some time, must be more than a month, the battery has 1 cell that deviates by 0.02v, all the rest are the same to 2 decimal places. So I won't have a balancer on it either ;-p.

 

[grinchy]

I would like to mention, as I don't think it was in this thread, and I did not mention it.... There is another way to fry your Alternator. If your BMS cuts the battery from the alternator, there is a possibility that as the load drops dramatically, the voltage spikes massively, thus burning out the diodes in the alternator and possibly sending significantly high voltage through your entire system.

This is not an issue for me, as a BMS is not needed in my setup. (I never thought I would say that...)
Still, it is worth knowing, if you were to use LiFepo4.
After some time, must be more than a month, the battery has 1 cell that deviates by 0.02v, all the rest are the same to 2 decimal places. So I won't have a balancer on it either ;-p.

There are snubbers/voltage arrest options for this on the market, they use a special diode called a tvs diode (if I recall) that can conduct the overcurrent away safely (I think via the ground) It does blow the diode, but they’re only $5 each or so. I got a few off of an electronics supply for my never finished install.

 

[Julez]

Are there really any starter batteries that have a BMS carrying the current, and not just a balancer? I mean, they must be able to withstand 1000A for a split second, and hundreds of Amperes for several seconds if a cold diesel engine does not start right away.

 

[sdnative]

Are there really any starter batteries that have a BMS carrying the current, and not just a balancer? I mean, they must be able to withstand 1000A for a split second, and hundreds of Amperes for several seconds if a cold diesel engine does not start right away.

Unlikely. Or at least it would have to be contactor based not FET based.

 

[Phoenix666]

Are there really any starter batteries that have a BMS carrying the current, and not just a balancer? I mean, they must be able to withstand 1000A for a split second, and hundreds of Amperes for several seconds if a cold diesel engine does not start right away.

There are options for a BMS that doesn't carry the current directly, but is able to disconnect the battery. While that would be unlikely, it is an easily accessible option, so I thought it worth mentioning. It is more likely to concern you if you charge your LiFePO4's off an alternator on a boat. As mine do not drift, I have discarded the balancer but left the connector for checking and perhaps balancing once every 6 months.

 

[Phoenix666]

Just tested the LTO starter with a LA car battery tester, which is essentially a 100amp load and a voltmeter that has a chart that shows what voltage a (x) CCA battery should sag to. Started at 14.1v as per normal, ran the test for 10 seconds, immediately sagged to 12.5 then stayed there rock solid the whole time.

If anyone is still interested and wants me to do any tests, let me know. I am a convert, but there are always more tests that can be done!

 

[veiloctane]

I noticed XS power has LTO batteries in there XV series. I may go this route instead of building my own.

XV Series Automotive Batteries Archives - XS Power Batteries

12V Lithium Titanate Automotive Batteries

4xspower.com

 

[Phoenix666]

I noticed XS power has LTO batteries in there XV series. I may go this route instead of building my own.

XV Series Automotive Batteries Archives - XS Power Batteries

12V Lithium Titanate Automotive Batteries

4xspower.com

You certainly could. You would be paying twice as much for half the ah, so 4x the cost? Although with the below I would replace the bus bars with something beefier.
The current (pun intended) LTO 12v* batteries are insanely priced. Probably still worth it in the long run, but only just. Unless you have specific needs, like cold temp starting etc.
I just tested my no-bms, no-balancer pack and 5 of the 6 cells are the same voltage to 3 decimal places, one cell deviates by 0.05v. This is after constan varied use for more than 6 months.

https://www.aliexpress.com/item/1005005945682418.html

Or go for rectangular cells to make fitment easier
https://www.aliexpress.com/item/1005004420515955.html this is likely what is inside the battery you mentioned. $120 USD, plus shipping.

 

[veiloctane]

You certainly could. You would be paying twice as much for half the ah, so 4x the cost? Although with the below I would replace the bus bars with something beefier.
The current (pun intended) LTO 12v* batteries are insanely priced. Probably still worth it in the long run, but only just. Unless you have specific needs, like cold temp starting etc.
I just tested my no-bms, no-balancer pack and 5 of the 6 cells are the same voltage to 3 decimal places, one cell deviates by 0.05v. This is after constan varied use for more than 6 months.

https://www.aliexpress.com/item/1005005945682418.html

Or go for rectangular cells to make fitment easier
https://www.aliexpress.com/item/1005004420515955.html this is likely what is inside the battery you mentioned. $120 USD, plus shipping.

Hey thanks for that info. I’m trying to understand why the Ah is only related 6Ah in the XV2400 and my AGM is 96Ah

I understand that AGM has only about 45-50% useable power but the LTO has about 90-100% useable power. Isn’t 6Ah almost nothing???

I do need cold cranking we can reach -40C easy here and I plan to use this in my diesel 80 series.

 

[Phoenix666]

Hey thanks for that info. I’m trying to understand why the Ah is only related 6Ah in the XV2400 and my AGM is 96Ah

I understand that AGM has only about 45-50% useable power but the LTO has about 90-100% useable power. Isn’t 6Ah almost nothing???

I do need cold cranking we can reach -40C easy here and I plan to use this in my diesel 80 series.

Well..... Ah is the total capacity, which is only half the picture. A SLA battery can discharge (safely) at about 3C, give or take. So if you are drawing 300A to start the car, a SLA must have an Ah rating of about 100Ah. The Ah is not as important as the ability of the battery to start a car.
On the other hand, LTO can discharge at 10C (or even higher), so a car needing a 300A start would only require a 30Ah LTO battery.
There are a bunch of other factors that make LTO even better, low voltage sag when discharging, very low self discharge, better cold weather performance, 20K cycles and so on.
My (anecdotal) evidence is how easily my car starts, compared to the proper CCA rated battery.

In regards to 6Ah being not a lot.... you would be correct. At 20C (not great for it) you could provide 120 amps, which would be very close to not starting even smaller cars. Perhaps that is for bikes?

From memory, -40C is getting close to LTO tolerance, it would be worth checking that, however it would always be better than SLA. With a battery heater that you could run via a remote switch, it should work just fine. I personally would probably "overkill" it with a battery heater that you can switch on and plug a jump-pack/usb power pack into it, then start it up after a few minutes of warming.

 

[veiloctane]

Looks like XS power lists sla Ah equivalent values. I was thinking of getting 2 but you may of convinced me to making my own.

XV2400 - XS Power

12-Volt LTO Battery Group 24 Cranking Amps: 670 Max Amps: 1,335 Wattage: 1,500 Amp Hours: 6 Equivalent AGM Amp Hours: 20 Rated up to 140°F Weight: 5.59 lbs. M6 Terminal Hardware Included Weighing in at just under seven pounds, the XS Power XV2400 Lithium Titanate Oxide (LTO) battery lasts up to...

4xspower.com

BCI	24
Voltage	12
Rated Watts	1500
Energy Wh	70
Max Amps	1335
Cranking Amps	670
CA Pb Eq	1000
Ah	6
Ah Pb Eq	20
Charge Current	10s Pulse – 200A, Continuous – 100A, Max Continuous – 150A
Terminal Orientation	Left Hand
Brand	XS Power Batteries

 

[Phoenix666]

Looks like XS power lists sla Ah equivalent values. I was thinking of getting 2 but you may of convinced me to making my own.

XV2400 - XS Power

12-Volt LTO Battery Group 24 Cranking Amps: 670 Max Amps: 1,335 Wattage: 1,500 Amp Hours: 6 Equivalent AGM Amp Hours: 20 Rated up to 140°F Weight: 5.59 lbs. M6 Terminal Hardware Included Weighing in at just under seven pounds, the XS Power XV2400 Lithium Titanate Oxide (LTO) battery lasts up to...

4xspower.com

BCI	24
Voltage	12
Rated Watts	1500
Energy Wh	70
Max Amps	1335
Cranking Amps	670
CA Pb Eq	1000
Ah	6
Ah Pb Eq	20
Charge Current	10s Pulse – 200A, Continuous – 100A, Max Continuous – 150A
Terminal Orientation	Left Hand
Brand	XS Power Batteries

The biggest thing I would worry about is drawing too hard on your alt. My use case means this is not an issue, and you can put a resistor on the alt to reduce the amount of amps it will put into the battery.

 

[veiloctane]

The biggest thing I would worry about is drawing too hard on your alt. My use case means this is not an issue, and you can put a resistor on the alt to reduce the amount of amps it will put into the battery.

Going to need a big resistor to drop my 390A alt down to 200A with this unless running 2batteries in parallel means it’s not needed but I’m not quite sure if it works like that.

 

[TeCKis300]

The Ah is not as important as the ability of the battery to start a car.

I beg to differ. Reserve is just as important a criteria if expecting any reasonable amount of standby time or accessory use while parked.

Assuming a nominal 80mA standby draw.

6Ah/.08A= 75hrs or 3 days parked to dead.


Assuming a conservative 15A in accessory mode.

6Ah/15A = .3hrs or 18 minutes of jamming out to the radio to dead.

 

[Phoenix666]

I beg to differ. Reserve is just as important a criteria if expecting any reasonable amount of standby time or accessory use while parked.

Assuming a nominal 80mA standby draw.

6Ah/.08A= 75hrs or 3 days parked to dead.


Assuming a conservative 15A in accessory mode.

6Ah/15A = .3hrs or 18 minutes of jamming out to the radio to dead.

This is true. I did say that 6Ah was not a lot and have been talking about 20-35Ah LTO, I guess I should have been more specific.

 

[Phoenix666]

Going to need a big resistor to drop my 390A alt down to 200A with this unless running 2batteries in parallel means it’s not needed but I’m not quite sure if it works like that.

TLR
IF you drive every couple of days AND you have a 20+Ah battery (LTO, not SLA) then you don't need to change anything.
Do NOT, under any circumstances, mix SLA and LTO (well, get a pro to tell you how to set up the dual batteries, then don't do it)

Something else I should have been more specific on!

The reason you would lower the output on the alt to the battery, is that if you run your alt at "max powa!" for too long it will overheat and die.
This is a (potential) problem for someone like me, who has a wimpy alt. If I charged my LTO from empty to full, assuming continuous (dangerous) heat is when it is producing 60 amps, it would potentially stay at that level for 30 minutes, which is very likely to fry it.

I don't worry about this, as mine in a daily driver and the start/idle draw is recharged within 10 seconds or less. I also don't worry, as due to the nature of charging, the closer the battery comes to the alt voltage, the less amps it draws. Also, as the alt heats up, it's ability to stay at 14.5v is limited, often down to 13.8v.

In your case, the issue is not an issue, as you have a beefy alt. Assuming it can charge at 400A, you will fill (from empty, which doesn't really happen), assuming 20Ah.. would be 1/20th (20/400A) of an hour, so 3 minutes.
Even at half that rate, it would take 6 minutes.
Half the rate, 30Ah LTO would take 9 minutes
You get the idea, those are the worst case scenarios, you would likely be drawing maybe 500A for 5 seconds cranking (again, worst case) so your recharge time would be maybe 2x the cranking time. As mentioned before, idle cars usually draw about 0.1 amps while sitting in your garage. So after 24 hours, you have lost 2.4Ah.

LTO also starts motors faster, as it doesn't voltage sag as much, nor does it waste energy doing float and crap.

 

[veiloctane]

TLR
IF you drive every couple of days AND you have a 20+Ah battery (LTO, not SLA) then you don't need to change anything.
Do NOT, under any circumstances, mix SLA and LTO (well, get a pro to tell you how to set up the dual batteries, then don't do it)

Something else I should have been more specific on!

The reason you would lower the output on the alt to the battery, is that if you run your alt at "max powa!" for too long it will overheat and die.
This is a (potential) problem for someone like me, who has a wimpy alt. If I charged my LTO from empty to full, assuming continuous (dangerous) heat is when it is producing 60 amps, it would potentially stay at that level for 30 minutes, which is very likely to fry it.

I don't worry about this, as mine in a daily driver and the start/idle draw is recharged within 10 seconds or less. I also don't worry, as due to the nature of charging, the closer the battery comes to the alt voltage, the less amps it draws. Also, as the alt heats up, it's ability to stay at 14.5v is limited, often down to 13.8v.

In your case, the issue is not an issue, as you have a beefy alt. Assuming it can charge at 400A, you will fill (from empty, which doesn't really happen), assuming 20Ah.. would be 1/20th (20/400A) of an hour, so 3 minutes.
Even at half that rate, it would take 6 minutes.
Half the rate, 30Ah LTO would take 9 minutes
You get the idea, those are the worst case scenarios, you would likely be drawing maybe 500A for 5 seconds cranking (again, worst case) so your recharge time would be maybe 2x the cranking time. As mentioned before, idle cars usually draw about 0.1 amps while sitting in your garage. So after 24 hours, you have lost 2.4Ah.

LTO also starts motors faster, as it doesn't voltage sag as much, nor does it waste energy doing float and crap.

wow this is alot of information to take in thankyou!!!!

 

[veiloctane]

lurking around I found this post for the round yinlong cells this guy posted his 3d print design for the endcaps

Builds - Airbagged 80 series on 42 inches. Low cost Russian build thread

Oh yeah, an LTO update! So they worked great for you all winter? No charging or starting or other weird problems--same as normal lead acid in terms of performance?

forum.ih8mud.com